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Wednesday - December 10, 2008

From: Dallas, TX
Region: Southwest
Topic: Shade Tolerant
Title: Grass to grow in the shade of pecan tree
Answered by: Nan Hampton

QUESTION:

Dear Mr. Smarty Pants, We have an enormous pecan tree in our backyard that had grass underneath the breadth of the branches, but not around the trunk. The grass isn't doing well (though we did fail to fertilize it last year) and I was wondering if there is a grass that can grow under the shady limbs of a pecan tree. Will the shade and juglones kill anything and everything off? Thanks so much!

ANSWER:

You are correct that the juglones that are produced by trees in the Family Juglandaceae (Walnut Family) are allelopathic to some, but not all, other plants. You can see lists of plants susceptible to juglones and those tolerant of juglones from Ohio State Univeristy. It appears that the level of juglone in Carya illinoinensis (pecan) is less than in walnuts. Grasses, in general, seem to be tolerant of juglones. In fact, there have been studies showing that bermudagrass and tall fescue are allelopathic to pecan seedlings!

Here are three grasses and a sedge that occur in the Dallas area and will grow in the shade. I have personal experience with inland sea oats growing quite happily under my walnut tree and suspect the other three species will also be tolerant of your pecan's juglones.

Chasmanthium latifolium (Inland sea oats)

Elymus canadensis (Canada wildrye)

Muhlenbergia schreberi (nimblewill)

Carex blanda (eastern woodland sedge)